Eros asteroid proves to be solid as rock

Nearby satellite disproves 'pile of rubble' hypothesis

Published: Friday, September 22, 2000

WASHINGTON {AP} Eros, a telephone-shaped asteroid that has been studied close-up for months by a satellite, is a solid, primitive chunk of rock scarred by craters and not a "pile of rubble" like some other asteroids, researchers say.

A spacecraft called Near Earth Asteroid Rendezvous, or NEAR, became the first to orbit an asteroid last February and instruments on the craft have probed the chemistry, density and surface features of the 21-mile-long rock. The results show that Eros is very old, perhaps as old as the Earth itself.

"We know now that the asteroid is a primitive body," Andrew F. Cheng, the NEAR project scientist at the Johns Hopkins University Applied Physics Laboratory. "It has never been melted, never separated into core, crust and mantle the way the Earth and the other inner planets have."

Papers summarizing the results of NEAR appear today in the journal Science.

Eros is a near-Earth asteroid, an orbiting space rock that passes close, but never crosses, the Earth's orbital path. Eros' orbit dips to within 105 million miles of the sun and then loops out to some 165 million miles from the sun. The Earth is about 93 million miles from the sun.

The NEAR was launched in 1996 and settled into an orbit of Eros, an asteroid named for the Roman god of love, on Feb. 14, 1999, St. Valentine's Day. The $224 mission is scheduled to end next February when the NEAR will be deliberately flown into Eros. Mission scientists hope for a soft landing.

Cheng said the solid character of Eros suggests it may have broken off as one chunk from a much larger body, perhaps another asteroid.